Mech 500 bionic implants and devices
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Functional Biomaterials for Bionic Implants. Design of Soft-Tissue vs. Hard Tissue ... Bionic Implants to be designed with Clinical and Market Realities in mind. ...

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MECH 500: Bionic Implants and Devices

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MECH 500:Bionic Implants and Devices

Sumitra Rajagopalan

sumitra.rajagopalan@polymtl.ca

Office Hours:

5pm – 5:30 pm Mondays

4 pm- 5pm Fridays


Bionic Implants & Devices: Overview

  • Layout of Course

  • Evaluation & Expectations

  • What is the course really about?

  • Course Prologue


Course Layout

  • Basic Notions in Medical Devices

  • Functional Biomaterials for Bionic Implants

  • Design of Soft-Tissue vs. Hard Tissue Implants

  • Implant Surfaces and Interfaces

  • Bioactive and Bioresponsive Implants

  • Functional Tissue Engineering and Bioartificial Organs

  • Bioelectrodes, Artificial Muscles and Neuroprosthetics

  • Brain-Machine Interface and Cortical Prosthetics

  • Implantable Devices for Minimally-Invasive Surgery

  • Biosensors, Bioelectronics, Closed-Loop Management

  • Getting Medical Device to Market: The Regulatory Environment

  • Introducing Bioastronautical Engineering


Course Evaluation

  • Class Participation: 15%

  • Critical Review of Article(s) OR Case Study #1: 20% (Assigned)

    Third week of September, due early November

  • Case Study # 2: 25% (Assigned or Chosen)

    Third week of October, due at the end of semester

  • Take-Home Exam (5 questions): 40%

    December 1st, due December 10th


What you will get out of the course:

  • A broad, comprehensive overview of the field

  • Study the human body from a materials/mechanical engineering perspective

  • Understand and appreciate differences between living and man-made materials and structures

  • Custom-design materials and structures to suit biological function : Biomimicry

  • Design appropriate material surface and interface

  • Identify optimal control & feedback system for implant

  • Understand and appreciate factors governing behaviour in-vivo

  • Basic design of biosensors and bioelectronic implants including Bio-mems and nems

  • Getting medical device to market

  • Apply knowledge of human factors engineering to extreme enviroments: outer space

  • Project ideas for Honour’s, M.Sc/PhD thesis

  • Learn the State-of-the-Art in the Field as well as Future Prospects


So, what is this course really about?


Medical Devices :A Multidisciplinary Enterprise

biology, physiology, biochemistry, immunology

Life Sciences

BIOMATERIALSBIOIMAGING BIONICS

BIOMECHANICS

BIOINSTRUMENTATION

electronics, image processing, mechanics,

chemistry, physics, materials, mathematics

Physical Sciences

Engineering


What is a Medical Device?

  • "an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including a component part, or accessory which is:

  • recognized in the official National Formulary, or the United States Pharmacopoeia, or any supplement to them,

  • intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals, or

  • intended to affect the structure or any function of the body of man or other animals, and which does not achieve any of it's primary intended purposes through chemical action within or on the body of man or other animals and which is not dependent upon being metabolized for the achievement of any of its primary intended purposes."

www.fda.gov


Why Bionic ?

1973

1976

1990

2000


Bionics: Inspired by Nature

  • Coined by Jack Steeles of the U.S. Air Force in 1960

  • Studying Nature from an Engineering/ Design Perspective

  • Extracting Structural, Design Paradigms.

  • Adopting these paradigms to solve a range of engineering problems.

  • Other names: Biomimicry,Biomimetics


Bionic Implant & Device

  • Implant that mimics – as far as possible – the structure AND function of the body part it replaces.

  • Interacts with the human body in a bidirectional fashion

  • Examples of Bionic Devices: Artificial Heart, Artificial Muscle, Cochlear Implant, Bioelectrodes, Mechanoactive Cartilage

  • Towards seamless integration of implant with physiological environment

  • Closed-loop system : Example of artificial pancreas.


Living vs. Man-Made: Reflections


Living Materials, Structures and Machines

  • Multifunctional Materials

  • Heirarchical, built through self-assembly

  • Ordered, patterned, nano-structured

  • Graded properties and functions throughout structure

  • Seamless integration of materials and structures of varying properties

  • Control & feedback integrated into structure

  • Adaptive

  • 3Rs: renewing, repairing, replicating

  • FORM FOLLOWS FUNCTION

  • FORM FITS FUNCTION


FORM FITS FUNCTION: Reflection

  • Cartilage?

  • Muscle?

  • Bone?

  • Skin?


Anatomy of an Implant: Design & Fabrication Considerations

  • Biomaterial

  • Bulk Structure

  • Interface

  • Implant Anchoring

  • Sterilisation Method

  • Power Issues in Implant Design

  • Wireless Monitoring of Implant


Biomaterials

Material intended for implanting in human body


Smart Materials: Bridging Materials to Life

  • Shape-memory foams

  • Shape-memory alloys

  • Polyelectolyte Hydrogels

  • Piezoelectric Ceramics

  • Electroactive Polymers

  • Self-healing composites

  • Supramolecular Chemistry


Bionic Devices: Behaviour in-vivo

  • Biocompatibility/Cytotoxicity

    • Ability to function in-vivo with no adverse immune reaction

  • Biodegradability

    • Break-down of biomaterial through action of body enzymes into non-toxic byproducts.

  • Biostability

    • Resistant to break-down in the human body

  • Biofunctionality

    • Functions as structure intended to replace


Inflammation & Immune System: Host Response

  • Inflammation occurs through foreign body response, movement of implant

  • Protein layer formed on implant surface

  • Even "inert" materials cause inflammation

  • Inflammation reaction can adversely affect both patient & the functioning of implant

  • Engineered biological tissue can cause adverse immune reaction

  • Still empirical


Solution? Surface Engineering

  • Biorecognisable implant surface

  • Designing templates with cell-adhesion molecules

  • Micro- and nano-texturing of surface

  • Porous Structures : Why?

  • Drug-eluting surfaces


Functional Tissue Engineering

  • Engineering Living Tissue on Synthetic Scaffolds

  • Scaffolds: porous, biodegradable, mimic the extracellular matrix

  • Several parameters at play : ?

  • Role of Mechanical Engineering: Develop mathematical models to describe tissue growth on scaffolds through these parameters

  • What’s the difference between tissue engineering and functional tissue engineering?

Boccafoschi, F et al. Biomaterials 26 (2005) 7410–7417


Interface with Excitable Tissue: Toward Neuromuscular Prosthetics

  • Excitable Tissue:Nerve, Muscle

  • Bioelectronic Devices are either stimulate/record biosignals (or both)

  • Electronic Implant consists of

    • Power Source

    • Controller

    • Stimulator

    • Electrode

  • Used in a wide range of pathologies: spinal cord injuries, parkinson’s disease, epilepsy, stroke etc.

  • Nerve-electrode interface remains the weakest link

  • Study of bioelectric phenomena crucial to developing biocompatible electronic implants.


Notions in Bioelectricity

  • Equivalent circuits used to model intefacial/ bioelectric phenomena

  • Impedance Analysis used to calculate parameters affecting charge transfer from device-tissue

    • Capacitance

    • Inductance

    • Resistance

  • Models derived used to design medical instruments, biosensors and other bionic devices

Zhu, F., Leonard,.E Levin,. N Physiol. Meas. 26 (2005) S133–S143


Wrap-up: Points to Remember

  • Highly multidisciplinary field drawing in on chemistry, biology, physiology, mechanics, electronics ….

  • Unlike the man-made world, Nature SEAMLESSLY integrates different components and functions into a working unit.

  • Biological materials vastly differ from man-made materials and that has to bet aken into account when designing implants

  • Bionic Implants emerge ONLY in response to a clinical PULL (need)

  • Bionic Implants to be designed with Clinical and Market Realities in mind.

  • Role of Mechanical Engineer: Interfacing with multiple disciplines, interacting with multiple professionals.


Carbon Nanotube Sheets for use as Artificial Muscles: Discussion Questions

  • Differing requirements for robotic vs. prosthetic applications

  • What are the advantages of carbon nanotubes?

  • What are their drawbacks?

  • Predict behaviour in-vivo

  • Follow-up to this work?


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